1. Field of the Invention
The invention relates to a printed wiring board and an electronic part to be mounted on a printed wiring board.
2. Description of the Related Art
FIGS. 1A and 1B illustrate a conventional printed wiring board.
In a conventional method, as illustrated in FIG. 1A, there is first fabricated a module 203 comprised of a module substrate 201 and parts 202 mounted on the module substrate 201. Then, as illustrated in FIG. 1B, the module 203 as well as other parts 211 are mounted on a printed substrate 210.
This conventional method has an advantage that since the module 203 15 is fabricated separately, the module 203 can be tested one by one as to whether they properly operate. Hence, only the module having been proved to properly operate can be mounted on the printed substrate 210, which ensures that a fabrication yield of the product illustrated in FIG. 1B can be enhanced, even if the module 203 has a low fabrication yield.
However, the above-mentioned conventional method has problems as follows.
It is possible nowadays to fabricate a module with a high fabrication yield. Hence, since the parts 202 have to be mounted on the module substrate 201 at a plurality of times in accordance with the above-mentioned conventional method, there would be caused problems that fabrication efficiency is unavoidably deteriorated, and that fabrication cost of the module substrate 201 is unavoidably high. In addition, since the module substrate 201 having sufficient strength as a unit is mounted on the printed board 210, there is caused another problem that the product illustrated in FIG. 1B is unavoidably high.
Japanese Unexamined Patent Publication No. 56-165389 has suggested a hybrid integrated circuit including a first substrate and a second substrate adhered to the first substrate. The second substrate has a different material from a material of which the first substrate is composed, and a different structure from that of the first substrate. A chip-shaped part is to be mounted on the thus adhered substrates. The first substrate is formed with a recess, and the second substrate is embedded in the recess.
Japanese Unexamined Patent Publication No. 7-30055 has suggested a printed wiring board wherein a multi-chip module substrate is fixed in a pit formed at a surface of the printed wiring board.
Japanese Unexamined Patent Publication No. 3-11739 has suggested an electronic device including an electrically conductive pattern formed on a circuit board, an electrode pad formed around a semiconductor chip in a specific area, and a metal bump electrically connecting the electrically conductive pattern to the semiconductor chip. A metal layer is formed between the semiconductor chip and the circuit board in an area other than the specific area. The metal layer has almost the same thickness as that of the metal bump, and is composed of the same material as a material of which the metal bump is composed.
Japanese Unexamined Patent Publication No. 5-267392 has suggested a multi-layered wiring substrate for electrically connecting semiconductor chips to each other through solder balls. Electrodes on which the solder balls are to be mounted are arranged in point and/or line symmetry about a center of a substrate.
Japanese Unexamined Patent Publication No. 9-298274 has suggested a method of mounting a semiconductor chip, including the steps mounting a semiconductor chip on a module substrate such that the semiconductor chip makes electrical contact with the module substrate, and mounting the module substrate on a printed substrate, characterized by the steps of forming a recess at a surface of the printed substrate in alignment with the semiconductor chip mounted on the module substrate, electrically connecting the module substrate to the printed substrate, and filling a gap between the module substrate and the printed substrate with sealing resin.